The long-term objectives of the proposed research program are to develop model systems for the study of molecular mechanisms of specific neuronal-glial interactions during brain development, and the consequences of these interactions for the differentiation of both cell types, including effects on the expression of developmentally regulated genes. The short-term goals and specific aims of the proposed project involve the use of a cell culture system to study the interactions between specific types of embryonic neurons, identified by transmitter phenotype (serotonergic, dopaminergic, GABAergic) and monolayers of mature astrocytes, fibroblasts, or embryonic glial cells (radial glia, astrocytes). The effects of such neuronal-glial interactions on the differentiation and survival of these transmitter-identified neurons will be measured both biochemically (high affinity uptake of 3H-transmitters) and morphologically (quantitation of cell number and morphometry of immunocytochemically stained neurons). A cell adhesion assay, currently under development, will be used to quantitate the adhesion of these neurons (radiolabelled with their own 3H-transmitter) to the same non-neuronal monolayers described above. It is hypothesized that distinct adhesion preferences may emerge from interactions between specific populations of transmitter-identified neurons and immature glial cells from the same brain region or gestational age. In future experiments, we hope to use the adhesion assay to test possible molecules mediating these neuronal-glial interactions, and the cell culture system to examine the effects of these interactions on gene expression in both neurons and glia using probes to cell-specific messages.